Propeller drive for watercraft

Abstract

A propeller drive for watercraft, preferably for ferry boats and car ferries, which has two propellers located one behind the other in the center-line plane. The forward propeller is preferably located on a marine shaft which exits the hull, and can be driven by means of a drive system. The aft propeller is preferably driven by means of a separate drive system, and the aft propeller is realized so that it can pivot by at least about 90 degrees around an axis, the axis being preferably vertical.

What is claimed is: 
     
       1. A propeller drive for an ocean-going ferry watercraft, the watercraft having a hull with a longitudinal axis, said propeller drive comprising: an aft propeller mechanism;   an aft propeller drive mechanism to drive said aft propeller mechanism;   a forward propeller mechanism;   a forward propeller drive mechanism to drive said forward propeller mechanism;   said aft propeller mechanism being configured to be disposed astern of said forward propeller mechanism;   an arrangement to pivot said aft propeller mechanism substantially greater than 90 degrees with respect to the longitudinal axis;   said aft propeller mechanism having a drive position to drive a watercraft forward; and   at least a portion of said aft propeller drive mechanism being disposed between said forward propeller mechanism and said aft propeller mechanism upon said aft propeller mechanism being disposed in said drive position.   
     
     
       2. The propeller drive according to claim 1, wherein: said aft propeller mechanism comprises a propeller; and   said propeller is configured to be disposed unshrouded into ambient seawater about the watercraft.   
     
     
       3. The propeller drive according to claim 2, wherein: said forward propeller drive mechanism and said aft propeller drive mechanism comprise an arrangement to jointly propel the watercraft;   said forward propeller drive mechanism comprises a first engine to drive said forward propeller mechanism; and   said aft propeller drive mechanism comprises a second engine to drive said aft propeller mechanism.   
     
     
       4. The propeller drive according to claim 3, wherein: said aft propeller drive mechanism and said forward propeller drive mechanism are separate and independent with respect to one another; and   each of said aft propeller drive mechanism and said forward propeller drive mechanism are configured and disposed to permit propulsion of the watercraft in the open ocean by solely one of said aft propeller drive mechanism and said forward propeller drive mechanism.   
     
     
       5. The propeller drive according to claim 4, wherein: said propeller comprises an aft propeller of said propeller drive;   said forward propeller mechanism comprises a forward propeller;   each of said aft propeller and said forward propeller are configured to be approximately equal in size with respect to one another; and   each of said first and second engines are configured to be approximately equal in power output with respect to one another.   
     
     
       6. The propeller drive according to claim 5, the hull of the watercraft having a waterline, the hull of the watercraft defining a central plane extending along the longitudinal axis of the hull, wherein: said first engine is configured to be disposed in the hull of the watercraft;   said forward propeller drive mechanism comprises a marine shaft;   said marine shaft extends between said first engine and said forward propeller to transmit torque from said first engine to said forward propeller;   said marine shaft comprises a portion configured and disposed to exit the hull of the watercraft;   said forward propeller is mounted on said portion of said marine shaft;   said aft propeller is configured to be disposed a first distance below the waterline of the watercraft;   said forward propeller is configured to be disposed a second distance below the waterline of the watercraft, the second distance being substantially equal to the first distance;   said arrangement to pivot said aft propeller mechanism is configured to pivot said aft propeller around a substantially vertical axis with respect to the waterline of the watercraft;   said arrangement to pivot said aft propeller mechanism is configured to orient the pivoting axis in substantially the central plane of the hull of the watercraft;   said forward propeller is configured to rotate about a first axis of rotation;   said aft propeller is configured to rotate about a second axis of rotation; and   each of the first axis of rotation and the second axis of rotation is oriented in substantially the central plane of the hull of the watercraft.   
     
     
       7. The propeller drive according to claim 6, said propeller drive further comprising: a rudder blade; and   said aft propeller mechanism is mounted on said rudder blade.   
     
     
       8. The propeller drive according to claim 7 wherein said aft propeller is disposed aft of said rudder blade. 
     
     
       9. The propeller drive according to claim 8, wherein at least one of said forward propeller and said aft propeller comprises a variable pitch propeller. 
     
     
       10. The propeller drive according to claim 9, wherein: said forward propeller drive mechanism comprises a first control system;   said forward propeller drive mechanism comprises a first steering system;   said aft propeller drive mechanism comprises a second control system; and   said aft propeller drive mechanism comprises a second steering control system.   
     
     
       11. A propeller drive for an ocean-going watercraft, the watercraft having a hull, the hull of the watercraft having a longitudinal axis, said propeller drive comprising: an aft propeller mechanism;   a forward propeller mechanism;   said aft propeller mechanism being configured to be disposed astern of said forward propeller mechanism;   an arrangement to pivot said aft propeller mechanism substantially greater than 90 degrees with respect to the longitudinal axis around an axis;   a first drive system for driving said forward propeller mechanism;   a second drive system for driving said aft propeller mechanism;   said first and second drive systems comprising an arrangement to jointly propel the watercraft on the open ocean; and   each of said first and second drive systems comprising an arrangement to independently propel the watercraft on the open ocean.   
     
     
       12. The propeller drive according to claim 11, wherein: said first and second drive systems are separate from one another to selectively permit each of said first and second drive systems to solely propel the watercraft on the open ocean;   said first drive system comprises a first engine to generate power to drive said forward propeller mechanism;   said second drive system comprises a second engine to generate power to drive said aft propeller mechanism;   said first engine is configured to permit propulsion of the watercraft on the open ocean solely by the power generated by said first engine; and   said second engine is configured to permit propulsion of the watercraft on the open ocean solely by the power generated by said second engine.   
     
     
       13. The propeller drive according to claim 12, wherein: said forward propeller mechanism comprises a forward propeller;   said forward propeller is configured to permit propulsion of the watercraft on the open ocean solely by said forward propeller being driven by said first engine;   said aft propeller mechanism comprises an aft propeller; and   said aft propeller is configured to permit propulsion of the watercraft on the open ocean solely by said aft propeller being driven by said second engine.   
     
     
       14. The propeller drive according to claim 13, wherein said aft propeller is an unshrouded propeller to permit said aft propeller to be disposed within ambient seawater. 
     
     
       15. The propeller drive according to claim 14, said propeller drive further comprising: a rudder blade being configured to be attached to the watercraft to form a rudder; and   said aft propeller is attached to said rudder blade.   
     
     
       16. The propeller drive according to claim 15, wherein said aft propeller is disposed astern of said rudder blade. 
     
     
       17. The propeller drive according to claim 16, wherein at least one of said forward and aft propellers comprises a variable pitch propeller. 
     
     
       18. The propeller drive according to claim 17, the hull of the watercraft having a waterline, the hull of the watercraft defining a central plane extending along the longitudinal axis of the hull, wherein: said first engine is configured to be disposed within the hull of the watercraft;   said first drive mechanism comprises a marine shaft;   said marine shaft extends between said first engine and said forward propeller to transmit torque from said first engine to said forward propeller;   said marine shaft comprises a portion configured and disposed to exit the hull of the watercraft;   said forward propeller is mounted on said portion of said marine shaft;   said aft propeller is configured to be disposed a first distance below the waterline of the watercraft;   said forward propeller is configured to be disposed a second distance below the waterline of the watercraft, the second distance being substantially equal to the first distance;   said arrangement to pivot said aft propeller mechanism is configured to pivot said aft propeller around a substantially vertical axis with respect to the waterline of the watercraft;   said arrangement to pivot said aft propeller mechanism is configured to locate the pivoting axis in substantially the central plane of the hull of the watercraft;   said forward propeller is configured to rotate about a first axis of rotation;   said aft propeller is configured to rotate about a second axis of rotation; and   each of the first axis of rotation and the second axis of rotation is oriented in substantially the central plane of the hull of the watercraft.   
     
     
       19. The propeller drive according to claim 18, the ocean-going watercraft comprising an ocean-going ferry, wherein: said first drive system comprises a first control control system;   said first drive system comprises a first steering system;   said second drive system comprises a second control system; and   said second drive system comprises a second steering system.